Heat-fusible safety link for insertion within a hot-air conduit of a heating system



Feb. 21, 1950 A. M. SMITH EI'AL 2,498,382

HEAT FUSIBLE SAFETY LINK FOR INSERTION WITHIN A HOT AIR CONDUIT OF A HEATING SYSTEM Filed March 25, 1946 FIG- l. a

Tier. 3.

Edward HQ/T & AM. J/fl/fh;

Gmmwu Patented Feb. 21, 1950 nEAT FUs-I-BLE SAFETY LINK FORVINSER- rr-on WITHIN 1A- HOT-AIR oonnmrona T: HEATING. SYSTEM Albert MI Smith and Edward Hart, Columbus, Ohio z'hzpplicatiori March-25, 1946,"Serial"No. 656,814

tion to providaa device. forautomatically clos ing the draft door of a-furnace, when. the-same hastbeen accidentally left-open. for. a. period of time sufficient. to. occasion. anuoverheating condition within: the furnace.

. It is another object of our invention to provide a device of: this characterwhich. structurally I imple. and consequently inexpensive: tomanufacre. It is af-urther object of our invention to provide a device of this. characterrwhich. may be easily installed and replaced withinany. standard. coal furnace Without-necessitating the services of a repairman. particularly: skilled in furnace operations.

For a further"and'moreicomplete understanding of our invention, reference is made to the following description and the accompanying drawings, wherein:

Fig. 1 is a diagrammatic elevational view show- F ing our. present improved heat-fusible linkoperportion of a hot air conduit in which the present heat-fusible link is operatively installed; and

Fig. 3 is a detailed perspective view of the present heat-fusible link.

With reference to the drawings, it will be seen that our invention embodies a fusible link comprising a V-shaped member ID formed of semiresilient metal wire, and a central hook element I I united with the V-shaped member ID, at its apex, by a fusible heat-softening material I2, such as solder having a comparatively low melting point. The central hook element I I also carries a circular stop collar I3 substantially above and beyond the arms of the V-shaped member ID.

In operation, the lower portion of the link is inserted through a small aperture I4 drilled-in one. of the. hot air conduits -I 5.of v a. furnace. in proximity totheplenum chamber I 5a.. Wheninserting. the-lower portion of the. link within the conduit, the armsof the resilient V-shaped memher It are squeezed together so as to permit of free entrancethrough the aperture. I4, and. once th upper ends of the arms are through the aperture andwithin.. the conduit, they will immediately. spring aparttotheir-normal position and thereby retairrthe l-ink. within. the conduit. Thus itwillbe seen thatthelower end of the link containing the soldered: union. willhbe maintained internally of the conduitand the outer hook element will be positioned. externally "thereof. by means of the action. of thcstop collar I3.

Normallya furnaceis supplied. with a remotely located manualv controlwhich operates, by means of chains andpulleys, the. draft'doori of the furnace In such. a. system, the pulleys. orguid'es-are usually. located. above thefurnace andlare attached to theunder surface. of a 'fl'oor".

In using our improved fusible link, the outer end of. the hookelement I I has bent engagement with one-end of. a. flexible. chain I6 which, in turn, is passed t-hrougha-screw eye I'll attached toa rafter or theunderside ofla. floor I8. The opposite end of the chainis. then rigidly attached to and supportsa detached-pulley -I8 substantially'in the same position-as the. latter would normally occupy when attachedto the rafter. Thus the normal manual. control. of' the draft door" isn'ot interfered-with. by the addition of our-safety solder union will melt same and free the hook element II. from the v -shaped' member I0, and

thus allow the pulley I 9" to'd'rop from its'normal position and allow the draft door to close.

To prevent the chain I6 and its attached pulley I9 from dropping completely to the floor upon the breaking of the link, a stop 20 is carried by the chain and positioned thereon so as to allow the pulley to drop only the distance sufficient for the closing of the door before the stop engages the screw eye I'I.

In View of the foregoing, it will be seen that our invention contemplates a highly efficient and structurally simple fusible link to be utilized as a safety feature for standard furnaces. It will also be noted that the installation of such a link may be easily accomplished utilizing the normally 3 installed equipment of a standard furnace, and that by simply drilling a small hole Within a hot air conduit, inserting the link, and attaching the chain to the pulley, the complete system may be accomplished by one not necessarily skilled in the repair or maintenance of furnaces. It will be manifest that the temperature at which the link will part may be controlled by the melting point of the fusible material used. It has been found desirable, when the link is positioned within the conduit, as shown in the drawings, that the melting point of the solder be in the neighborhood of 260 F.; however, it will be understood, in view of the following claims, that our invention is neither limited by the positioning of the link with respect to the various parts of the furnace, nor is it limited by the use of any one fusible material as each of these factors are necessarily dependent on one another, and may be varied to adapt the link for use under individual circumstances.

While we have disclosed what we now deem to be the preferred form of our improved fusible link, it will be manifest that various changes in design and details of construction may be later accomplished without departing from the spirit of the invention or the scope of the following claims.

We claim: r

1. In combination with a hot air conduit of a furnace, a fusible link comprising an elongated metallic rod formed at one end with a hook, and a V-shaped barb member united with the opposite end of said rod by a fusible heat-softening material, said barb member being located within said conduit and being formed with a pair of angularly related resiliently movable arms extending backwardly along said rod and terminating in end portions disposed in spaced longitudinal angular relation to said rod, the arms of said barb member being resiliently movable into substantially parallel positions alongside of said rod to permit insertion thereof through a.relatively small opening formed in said conduit, and when once inserted being adapted to spring apart and engage the inner wall of the conduit to prevent withdrawal of said link through such opening prior to the softening of the material uniting said barb member with said rod.

2. A heat fusible link for insertion within a hot air duct of a furnace system, comprising an elongated rod formed at one end with a hook, and a V-shaped barb member united at its apex with the opposite end of said rod by a fusible heat-softening material, said barb member being formed with a pair of resilient spring arms radiating outwardly from the apex of said member and backwardly in longitudinal angular relation to said rod and terminating in normally spaced apart relation intermediate the length of said rod, the arms of said barb member being resiliently movable toward one another into substantial parallelism with said rod to permit of insertion of said link through a relatively restricted opening formed in a hot air duct, and being separable under resilient tension after initial insertion within the air duct to retain said link therein against withdrawal.

3. A fusible link for insertion within a hot air conduit of a furnace system, comprising asubstantially straight metallic rod formed at one end with a hook, and a V-shaped barb member united at its apex with the opposite end of said rod by a heat-fusible material and having a pair of resiliently movable arms radiating backwardly along said rod and terminating in end regions disposed in normally spaced longitudinal angular relation to the'intermediate portion of said rod, the arms of said barb member being resiliently movable toward one another and into substantial parallelism with said rod to permit of insertion of said arms througha relatively restricted opening formed in a hot air conduit and to cause said arms to spring apart to their spaced angular positions with respect to said rod after insertion thereof within the hot air conduit to prevent withdrawal of said link from the conduit prior to the softening of the material uniting said barb member with said rod. 1

4. A fusible link for insertion within a hot air conduit, comprising a substantially straight rod provided at one end thereof with a' hook, and a barb device carried at the opposite end of said rod by means of a heat-fusible material and formed with a pair of angularly related resiliently movable arms extending backwardly along said rod and terminating intermediately thereof in spaced angular relation to said rod, the arms of said barb device being resiliently compressible toward one another and into substantial parallelism with respect to said rod to permit the barb-carrying end of said rod to be inserted through a relatively restricted opening formed in the wall of a hot air conduit and to permit the arms of said barb device to spring apart after passing through the wall of'the conduit to retain said rod against withdrawal therefrom prior to the fusing of the The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,688,121 Larson Oct. 16, 1928 1,765,243 Rowley June 1'7, 1930 1,894,425 Roessner Jan. 17, 1933 

